Baby bottles having flexible nipples are commonly used to feed infants and children milk, formula, juices and other fluids. During use, however, as the baby sucks on the nipple and withdraws the fluid, a partial vacuum is formed within the bottle. This vacuum can make feeding more difficult, by requiring the baby to suck with much greater force, which can discourage the baby and cause it to stop feeding sooner than desired. Moreover, the vacuum can cause the nipple to collapse.
To address this problem, a variety of vented bottle assemblies have been developed. One such method involves the use of a perforated elastomeric diaphragm attached to the bottom of the bottle. This diaphragm allows air in to alleviate the vacuum when the bottle is inverted and fluid is withdrawn. When the bottle is upright, however, and fluid is resting on the diaphragm, the perforations are effectively sealed and fluid does not pass through the perforations.
This bottle assembly, and a related process for equalizing pressure in a bottle, are disclosed and claimed in U.S. Pat. No. 5,499,729 to Greenwood et al., which issued on Mar. 19, 1996. The teachings of that patent are herein incorporated by reference. The bottle assembly claimed in the Greenwood et al. patent provides excellent vacuum control and fluid flow, in combination with ease of cleaning. However, the structure as disclosed in the Greenwood et al. patent suffers from one drawback. The diaphragm is merely pressed into engagement with the cap, and is only loosely retained therein by the threads of the cap before the cap is screwed onto the bottle. It is not affixed to the cap. While fluid does not leak through the multiple perforations in the central portion of the diaphragm, many users have experienced leakage due to improper placement of the diaphragm in its securing cap. If the elastomeric rim of the diaphragm is not replaced properly in the cap after cleaning, a seal will not form between the bottom lip of the bottle, the diaphragm's rim, and the cap. Fluid will then leak around the diaphragm and out of the air holes in the cap. Moreover, the typical user may not understand what is causing the leakage, and may wrongly attribute it to the perforations in the diaphragm. In addition, the loose diaphragm, separate from the remainder of the assembly, may be found and swallowed by a small child.
Accordingly, an improved bottle assembly is required that ensures that the diaphragm is properly and sealingly seated in the cap, to prevent leakage of fluid from the assembly. Moreover, such an improved assembly permits a user to disassemble and reassemble conveniently and without the concern that leakage will occur due to misalignment.